This is what the recipient of the note had to say:
... [T]his student finished the course fully five months ago. The assignment was due seven months ago. She didn’t take an extension or explain why it wasn’t done; she didn’t question the grade in December. I had forgotten she ever existed.
I am… I don’t know what I am. Baffled? Horrified? Insulted?
Link via Kieran Healy, who calls it a 'hall of fame note'.